Not Applicable
Not Applicable
Not Applicable
The present invention relates to expansion valves for controlling flow in a refrigerant system between the exothermic heat exchanger or condenser and the endothermic heat exchanger or evaporator and particularly relates to such systems as employed in air conditioning systems for the passenger compartment of motor vehicles.
Known techniques for operating a refrigerant expansion valve include utilizing a liquid filled capsule having a diaphragm responsive to changes of pressure in the capsule due to changes in the temperature of the liquid in the capsule which is in thermally conductive relationship with the refrigerant flowing through the valve and operable to move a valve member for controlling the flow from the high pressure inlet side, connected to the condenser, to the low pressure outlet connected to the evaporator. Such valves although currently popular in high volume production motor vehicle air conditioning systems have the disadvantage that the valve is only reactive to temperature changes in the system and cannot be controlled by an electrical signal provided from a computerized electronic controller. However, it is also known to add an electrically operated solenoid type valve upstream of the diaphragm operated valve in order to provide complete shutoff of the refrigerant flow through the expansion valve to prevent logging or flow in a dual evaporator system.
However, such combination solenoid operated shutoff valve and thermostatic expansion valve have been found to exhibit flow noise through the valve which has been unacceptable to the occupants of the vehicle. Accordingly, it has been desired to provide a way or means of reducing flow induced noise in a refrigerant expansion valve, and particularly one of the type having a solenoid operated shutoff valve combined therewith as employed in motor vehicle air conditioning systems.
The present invention provides a thermally responsive expansion valve for controlling flow in a refrigerant system and is of the type including a solenoid operated shutoff valve incorporated in a common valve block with the flow control valve. The valve block has an inlet adapted for connection to high pressure refrigerant from a condenser and an outlet for providing flow at a reduced pressure adapted for connection to an evaporator. A first restricting orifice is provided in the inlet upstream of the solenoid operated shutoff valve; and, a second restricting orifice of about the same size is provided in the solenoid operated shutoff valve, the results of which are reduced flow noise in the valve when the solenoid operated valve is open and the thermally responsive flow control valve is functioning for varying the flow therethrough. The valve assembly of the present invention is of the well known configuration having a return flow passage through the valve body into which a temperature responsive portion of the flow control valve operator connected to the diaphragm is immersed for temperature sensing.
The noise reducing orifices of the present invention may be conveniently provided between the inlet port and a cross passage for the first orifice and through the valve seat in the shutoff valve for the second orifice.